More exchange and transport systems: The heart

Question 1

What is the heart made of

Answer 1

Cardiac muscle

Question 2

What are the properties of cardiac muscles making it suited to its function

Answer 2

• It is myogenic - it can contract and relax without any nervous or hormonal stimulation
• It never fatigues as long as it has a supply of oxygen

Question 3

What are coronary arteries

Answer 3

Blood vessels that supplies the cardiac muscles with oxygenated blood

Question 4

What would happen if the coronary arteries were blocked

Answer 4

• The cardiac muscle would not receive oxygen
• Therefore cells will not be able to respire and will die
• this cause a myocardial infarction (a heart attack)

Question 5

Why is the heart described as a double pump

Answer 5

• The right side pumps deoxygenated blood to the lungs
• The left side pumps oxygenated blood to the whole body

Question 6

What are the atrioventricular valves

Answer 6

They are valves that link the atria to the ventricles

Question 7

What is the role of the atrioventricular valve

Answer 7

Allow blood to flow from the atria to the ventricles, but prevents blood flowing back into the atria when the ventricles contract

Question 8

What are semi-lunar valves

Answer 8

Valves that link the right ventricle to the pulmonary artery and the left ventricle to the aorta

Question 9

State the role of semi-lunar valves

Answer 9

Allow blood to flow from the ventricles to the pulmonary artery and the aorta, but prevents blood flowing back into the heart after the ventricles contract

Question 10

Why is the left ventricle thicker than the right ventricle

Answer 10

• The left has more muscular walls, bc it has to contract more powerfully to pump blood all the way around the body

WHEREAS

• The right side of the body is less muscular because its contractions are only powerful enough to pump blood to the lungs

Question 11

Which side of the heart is thicker

Answer 11

The left

Question 12

Why are the ventricles thicker than the atria

Answer 12

• Bc the ventricles need to pump blood out of the heart

WHEAEAS

• The atria has to only pump blood a short distance into the ventricles

Question 13

What are cords (in the heart)

Answer 13

Strong, fibrous connections attaching the AV valves to the ventricle to stop them being forces up into the atria when the ventricles contract

Question 14

What are the artria

Answer 14

Heart chambers that receive blood, then drives it into the ventricle

Question 15

What are the ventricles

Answer 15

Muscular chamber that pumps blood out of the heart and into the circulatory system

Question 16

What is the cardiac cycle

Answer 16

Ongoing sequence of contraction and relaxation of the atria and ventricle that keeps blood circulating around the body

Question 17

What are the three stages of the cardiac cycle

Answer 17

• Atrial systole
• Ventricular systole
• Ventricular diastole

Question 18

Describe what happens in atrial systole

Answer 18

• The atria contracts (the ventricles relaxes) - decreasing the volume w/in the chambers and increasing the pressure w/in the chambers
• Atrioventricular valves open, as the pressure pushes/forces the blood into the ventricles - causing a slight increase the ventricular pressure and volume as the ventricle receives the blood

Question 19

Describe what happens in ventricular systole

Answer 19

• The ventricles contracts (the atria relaxes) - decreasing its volume and increasing the pressure w/in the chambers
• Semi-lunar valves are forced open and blood is forced out into the pulmonary artery and the aorta
• Atrioventricular valves are forced close to prevent backflow - as the pressure of the ventricles is greater than of the atria

Question 20

Describe what happens in ventricular diastole

Answer 20

• The ventricles and the atria relaxes
• Semi-lunar valves are forced closed to prevent backflow of blood into the ventricles from the pulmonary vein and the artery
• Blood re-enters the atria due to the high pressure in the pulmonary vein and vena cava
• Atrioventricular valves are forced open, bc as the ventricles continue to relax the pressure falls below the pressure of the atria
• This allows blood to flow passively (without any contraction) into the ventricles from the atria
• Then atria contracts again (restarting the cardiac cycle)

Question 21

Describe the passage of blood through the right side of the heart

Answer 21

(superior and inferior) Vena Cava → Right atrium → Right AV valve → Right ventricle → Semi lunar valve → Pulmonary Artery

Question 22

Describe the passage of blood through the left side of the heart

Answer 22

Pulmonary vein → Left atrium → Left AV valve → Left ventricle → Semi lunar valve → Aorta

Question 23

When will a valve open

Answer 23

When the pressure BEHIND the valve is greater than the pressure in front of the valve

Question 24

What is the importance of valves only opening when the pressure is high behind them than in front

Answer 24

So that blood flows in one direction (so it is unidirectional)

Question 25

Define systole

Answer 25

The contraction of the heart muscles

Question 26

Define diastole

Answer 26

The relaxation of the heart chambers

Question 27

When do the atrioventricular valves open

Answer 27

• When the pressure in ventricles has fallen below pressure in atria

AND

• When the pressure behind valve (in the atrium) is greater than in front

Question 28

When do the semi-lunar valves open

Answer 28

• When the pressure behind valve (in the ventricle) is greater than in front

Question 29

What is the equation for cardiac output (include units)

Answer 29

Cardiac output (cm³ mins⁻¹) = stroke volume (cm³) x heart rate (bpm)